In a purely literal sense Bosola's role is that of the hired assassin. More fundamentally, he represents the repentant sinner by the end of the play; he moves from performing cold-blooded acts of murder, simply for money, to commentating on violence and evil. He does not turn good altogether and dies in misery and confusion, but his move towards repentance throws into sharp relief the greater villainy of the the Cardinal and Ferdinand - particularly the former.